Fuse



Jan, 12, 1960 P. A. DAHLEN FUSE Filed June 4, 1958 FIG.3

INVENTOR.

PAUL A.DAHLCN United States Patent FUSE Paul A. Dahlen, Mansfield, Ohio,assignor to Stevens Manufacturing Company, Inc., a corporation of 01110Application June 4, 1958, Serial No. 739,769

9 Claims. (Cl. 200117) The invention relates in general to an electricalfuse and more particularly to a fuse structure which is consistent andreliable in its operation.

Electrical fuses are placed in electrical circuits as a safety link toprotect thecircuit upon occurrence of some dangerous condition either inthe electrical device, or the electrical supply source, or both. Fusesare devices which have some form of a fusible material which will meltupon the occurrence of the dangerous condition such as an overload ofcurrent or excess heat to thus open the electrical circuit. Many fusesare constructed of a ribbon or wire of a low melting point alloy whichis so proportioned in size and shape as to melt upon a given excess ofcurrent for a particular voltage rating. In modern manufacturingtechniques many variables are encountered and it has many times beenobserved that fuses do not always function to interrupt the electricalcircuit at exactly the same value of current or the same value of theother variable determining the operation. Many devices are capable ofexamination after failure to determine the cause of failure, but a fuseinherently is extremely difiicult to examine after failure to determinethe cause of failure because by its very nature it destroys itself inoperation. The fusible element used in any fuse is subject to manyvariables such as poor electrical connection to the terminalconnections, various cross sectional area actually in use at any seriesconnected point in the circuit, impurities in the fusible material,variations in stress on the fusible material, impurities at the terminalconnections, etc. With these many variables many prior art fuses havebeen subject to considerable variation in operating pointwhen they weresupposedly all calibrated by size and shape for a particular operatingpoint.

Accordingly, an object of the invention is to provide a fuse structurewhich is capable of consistent and reliable operation.

Another object of the invention is to provide a fuse wherein thevariables affecting the operation are maintained at a minimum.

Another object of the invention is to provide a fuse wherein anyimpurities in the fusible material and any stressing of the fusiblematerial and any impurities on the terminal connections of the fusiblematerial have negligible affect on the operational characteristics.

Another object of the invention is to provide a fuse wherein a pluralityof areas of fusible material are all connected in parallel in theelectrical circuit and connected in parallel in the mechanicalarrangement.

Other objects and a fuller understanding of this invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawing, in which:

Figure 1 'is a side elevational view of a fuse embodying the invention;

Figure 2 is a front elevational view of the fuse; and

' Figure 3 is an isometric view of the fuse.

Figures 1 and 3 show different views of a fuse struc ture 11 which ismounted on a base 12, which base may be of insulating material. The fuseincludes generally first and second operating portions 13 and 14 carriedon the base 12 and, as shown in the drawing, these operating portions 13and 14 are carried on blades 15 and 16, respectively. The blades 15 and16 may for convenience and economy be made of one-piece construction;and also for economy, ease of assembly, and minimization of parts, theymay be made identical. The blade 15 has a first or terminal end 19, andthe operating portion 13 is at the second end thereof. The second blade16 has a first or terminal end 20, and the second operating portion 14is at the second end thereof. Each blade hasfirst and second right anglebends 21 and 22 in opposite directions to form a shoulder 23therebetween. The base 12 has first and second slots 24 and 25 shaped tofit the cross sectional shape of the blades 15 and 16. Rivets 26 passthrough the base 12 and the shoulders 23 to fasten the blades at theshoulders 23 to a first side 27 of the base 12. The blades 15 and 16 bypassing through the slots extend on a second side 28 of the base 12. Theterminal ends 19 and 20 may be of any suitable shape for providingelectrical connection into the electrical circuit with which the fuse 11is used, and in the drawing these terminals are shown as spade typeterminals.

The blades 15 and 16 are of strip material, that is, they are elongatedand are resilient current carrying conductors. The operating portions 13and 14 may be, and preferably are, identical with the operating portion13 having first and second legs 31 and 32, and the second operatingportion 14 having first and second legs 33 and 34. Each of theseoperating portions 13 and 14 is generally in the form of a U-shape tosupport the legs on the respective blade.

The blades 15 and 16 normally extend generally parallel to each other onthe second side 28 of the base 12 caused by their shape in being formed,their natural resilience, and the positioning during mounting on thebase 12. This inherent position of the blade 15 is shown in dotted linesin Figure 1. During manufacture the two operating portions are heldtogether against the resilient urging of the blades 15 and 16, andsolder 35 or other fusible material is caused to interconnect theoperating portions 13 and 14. Thus, the solder 35 appears in threediscreet areas interconnecting the side surfaces of the four legs 31-34.

The legs on each operating portion are substantially parallel to eachother and extend generally perpendicularly to the plane of therespective blade. Since the blades 15 and 16 are mounted so that theyare nominally parallel, this means that all four legs are generallyparallel. This further means that the urging means caused by thestressing of the blades 15 and 16 urges apart the operating portions ina direction substantially parallel to the planes of the legs 31-34. Thisestablishes substantially only a shear stress in the solder or otherfusible material 35. Previous fuse structures have been made whichsubject the fusible material to primarily a tension stress and usingonly a single mass of fusible material under stress, this means that ifany portion of the fusible material is of smaller cross sectional areaor contains impurities, this causes it to be the weakest link in thechain and will cause the fuse to fail, that is, operate, at a lowertemperature or current rating than desired.

The present invention by utilizing a plurality, in this case three, ofareas of solder which are mechanically stressed primarily in shear, thislikelihood of false operation or malfunctioning is practicallyeliminated. These three areas mechanically stressed in shear alsoestablish that there are three paralleled electrical paths between.

the first and second operating portions 13 and 14 which carry current;and hence, all three areas of fusible material must be melted before thefuse will operate.

The fuse 11 may be used in several different applications and onesuitable application is. one in which the temperature of theambientatmosphere is being controlled. Electrical current is necessarilypassed through the fuse 11 with the fuse controlling this electricalcurrent. The blades 15 and 16 may be made from beryllium copper, forexample, which is a good conductor of electricity as well as having goodelastic properties to maintain the resilient stress. In such case it isa relatively simple matter to proportion the current carrying parts ofthe fuse 11 so that the heating effect caused by the passage of currentthrough the fuse is small relative to the heating effect of the entirefuse caused by the ambient atmosphere. In such case, upon thesurrounding air becoming overheated, the fuse 11 will be actuated, thatis, to melt the solder 35, so that the blades 15 and 16 spring apart andhence interrupt the electrical circuit to relieve the cause of theoverheating of the ambient atmosphere. By making the two blades 15 and16 of unitary construction and identical, this permits the fuse to becheaply and quickly manufactured and assembled and minimizes theinventory of .parts necessary for con struction as well as providing forready interleaving of the legs 31 and 32 with the legs 33 and 34. Thefact that the solder 35 is in three separate areas means that should anyimpurities exist either in the solder-itself or on the side surfaces ofthe legs 31-34, such impurities or other causes of improper electricalconnection between the fusible material and the operating portions 13and 14 will have negligible affect on the operational characteristic ofthe fuse 11 because of the plurality of paralleled paths both electricaland mechanical.

Although this invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:

1. A fuse structure, comprising, a base, first and second operatingportions each having a pair of legs, means mounting said first andsecond operating portions on said base in mutually insulatedrelationship with said legs extending in spaced side-by-siderelationship, means providing electrical connection to each saidoperating portion, said operating portions being positioned tointerleave said legs, a mass of fusible material interengaging said fourlegs in the three areas between the side surfaces of said legs, andmeans urging apart said operating portions in a direction "substantiallyparallel to said side surfaces, whereby upon overheating said mass meltsto permit said operating portions to spring apart to open the electricalconnection therebetween.

2. A fuse structure, comprising, a base, first and sec ond substantiallyidentical blades, each blade being elongated with first and second ends,means mounting each said first end to said base, first and secondoperating portions each formed by a pair of legs, means mounting saidfirst and second operating portions to said first and second blades,respectively, in mutually insulated relationship, means providingelectrical connection to each operating portion, the two pairs of legsextending Substantially parallel, said second ends of said blades beingpositioned to interleave said legs, a mass of fusible materialinterengaging said four legs in the three areas between the sidesurfaces of said legs, and means urging apart said operating portions ina direction substantially parallel to the planes of the legs, wherebyupon overheatingsaid mass melts to permit said operating portionstospring.

apart to open the electrical connection,therebetween.

3. A fuse structure, comprising, an insulated base, first and secondsubstantially identical blades, each blade being elongated with firstand second ends, means mounting each said first end to said base, meansproviding electrical connection to said blades, a pair of legs on eachsaid second end forming an operating portion with the pair of legs ofeach portion extending generally transversely to the plane of therespective blade, the two pairs of legs extending substantiallyparallel, said second ends of said blades being positioned tointer-leave said legs, a mass of fusible material interengaging saidfour legs in the three areas between the side surfaces of said legs, andmeans urging apart said operating portions in a direction substantiallyparallel to the planes of said legs to load said fusible materialsubstantially only in shear, whereby upon overheating said mass melts topermit said second ends of said blades to spring apart to open theelectrical connection therebetween.

4. A fuse structure, comprising, an insulated base, a blade of resilientmaterial and elongated with first and second ends, means mounting saidfirst end to said base, first and second U-shaped portions each formedby a pair of legs, means mounting said first U-shaped portion on saidblade second end with a pair of legs extending generally transversely tothe plane of said blade, means mounting said second U-shaped portion onsaid base with the two pairs of legs extending toward each other andextending substantially parallel, means providing electrical connectionto each said U-shaped portion, said second end of said blade beingdeflected toward said second U-shaped portion to resiliently stress saidblade and to interleave said legs, and solder interengaging said fourlegs in the three areas between the side surfaces of said legs, thestressing of said blade loading said solder in shear, whereby uponoverheating said solder melts to permit said second end of said blade toresiliently spring away from said second U-shaped portion to open theelectrical connection therebetween.

5. A fuse structure, comprising, an insulated base, first and secondsubstantially identical blades, each blade being elongated with firstandsecond, ends, means mounting each said first end to said base, meansproviding electrical connection to said blades, a pair of legs on eachsaid second end forming a U-shaped portion, with the pair of legs ofeach portion extending generally transversely to the plane of therespective blade, the' two' pairs of legs extending toward each otherand extending substantially parallel, said second ends of said bladesbeing positioned to interleave said legs, solder interengaging said fourlegs in the three areas between the side surfaces of said legs, andmeans urging apart said U- shaped portions in a direction substantiallyparallel to the planes of said legs to load said solder in shear,whereby upon overheating said solder melts to permit said second endsofsaid blades to spring apart to open the electrical connectiontherebetween.

6. A fuse structure, comprising, an insulated base, first and secondsubstantially identical blades, each blade being of resilient materialand elongated with first and second ends, means mounting each said firstend to said base to establish said second ends spaced apart, terminalson said first ends of said blades for electrical connection, a

U-shaped portion formed on each said second end withthe pair of legs ofeach portion extending generally perpendicular to the plane of therespective blade, t-he two pairs of legs extending toward each other andextending substantially parallel, said second ends of said blades beingdeflected toward each other to resiliently stress said blades and tointerleave said legs, and solder interengaging said four legs in thethree areas between the side surfaces of said legs, whereby uponoverheating said solder melts to, permit said second ends of said bladesto resiliently spring apart to open the electrical connectiontherebetween.

7. A fuse structure for use in an electrical circuit, cornprising, aninsulated base, first and second substantially identical blades, saidblades being of resilient material, each blade being elongated andhaving first and second ends, means mounting each said first end to saidbase, terminals on said first ends of said blades for electricalconnection of said fuse structure in said circuit, the mounting of saidfirst ends of said blades establishing said second end-s spaced apart, aUz-shaped portion formed on each said second end with the pair of legsof each portion extending generally perpendicular to the plane of therespective blade, the two pairs of legs extending toward each other andextending substantially parallel, said second ends of said blades beingdeflected toward each other to resiliently stress said blades and tointerleave said legs, and solder interengaging said four legs in thethree areas between the side surfaces of said legs, whereby uponoverheating said solder melts to permit said second ends of said bladesto resiliently spring apart to open said electrical circuit.

8. A fuse link for use in an electrical circuit, comprising, aninsulated base, first and second substantially identical blades, saidblades being of elongated resilient material, each blade having firstand second ends, each said first end being a mounting end, saidinsulating base having first and second parallel and spaced slots shapedto receive said blades, first and second sides on said base, said bladespassing through said slots and having a portion lying against said base,fastening means passing through said insulating base and each saidportion to fasten each said blade to said base, terminals on said firstends of said blades for electrical connection of said fuse link in saidcircuit, the mounting of said first ends of said blades establishingsaid second ends spaced apart, a U- shaped portion unitarily formed oneach said second end with the pair of legs of each portion extendingsubstantially perpendicular to the plane of the respective blade, thetwo pairs of legs extending toward each other and extendingsubstantially parallel, said second ends of said blades being deflectedtoward each other to resiliently stress said blades and to interleavesaid legs, and solder inter-engaging said four legs in the three areasbetween the side surfaces of said legs, the stressing of said bladesloading said solder in shear, whereby upon overheating said solder meltsto permit said second ends of said blades to resiliently spring apart toopen said electrical circuit.

9. A fuse link for use in an electrical circuit, comprising, aninsulated base, first and second unitary identical blades, said bladesbeing of substantially flat resilient strip material, each blade havingfirst and second ends, each said first end being a mounting end andincluding first and second right angle opposite bends to form a shouldertherebetween, said insulating base having first and second parallel andspaced slots shaped to receive said blades, first and second sides onsaid base, said shoulder of each said blade engaging said first side ofsaid base, rivets passing through said insulating base and each saidshoulder to fasten each said blade to said base, terminals on theprotruding first ends of said blades for electrical connection of saidfuse link in said circuit, the mounting of said first ends of saidblades establishing said second ends resiliently extending substantiallyparallel to each other, a U-shaped portion unitarily formed on each saidsecond end with the pair of legs of each portion extending substantiallyperpendicular to the plane of the respective blade, the two pairs oflegs extending toward each other and extending substantially parallel,said second ends of said blades being deflected toward each other toresiliently stress said blades and to interleave said legs, and solderinter-engaging said four legs in the three areas between the sidesurfaces of said legs, the stressing of said blades loading said soldersubstantially only in shear, whereby upon overheating of the ambientatmosphere around said fuse link said solder melts to permit said secondends of said blades to resiliently spring apart to open said electricalcircuit.

References Cited in the file of this patent UNITED STATES PATENTS2,284,291 May May 26, 1942 2,457,941 Szabo Jan. 4, 1949 2,599,441 EkmanJune 3, 1952 2,791,660 Sims et al. May 7, 1957 FOREIGN PATENTS 609,745Great Britain Oct. 6, 1948 747,185 Great Britain Mar. 28, 1956

